If all I could get pre-stretched was a 20" x 24" frame then I would buy just one then make or have made some hard wood (or metal) frames about 9" x 11" on the outside. I would glue them to the mesh of the large frame then when the glue had set, cut them out individually.
Originally Posted by wildbillbugman
It would be a waste of a large frame but you would end up with some more manageable screens.
I'm not sure what glue to suggest for home use. We us a UV cure glue in our stretching room. Just shine some UV light at it for a few minutes and it's cured.